1. Field of the Invention
This invention relates to a semiconductor device having an internal power supply circuit, which can change an internal-power-supply-voltage.
2. Description of the Related Art
A substrate voltage detecting circuit is used especially to supply a stationary and stable substrate voltage to a cell array portion of a dynamic memory having a triple well.
In general, such substrate voltage detecting circuit is used only to detect a certain voltage. However, increasing miniaturization and integration of semiconductor devices in recent years have resulted in a drastically longer time for conducting tests. Accordingly, for the purpose of ensuring productivity, it is necessary to shorten such test time. To achieve this object, it is necessary to implement accelerated tests by increasing the internal voltage.
In Japanese Laid-open Public Hei 4-15949, a voltage conversion circuit comprising a reference voltage generating means for generating a plurality of reference voltages at different levels out of an externally supplied power supply voltage, a selection means for selecting one of said plurality of reference voltages in response to an externally given control signal and an outputting means for supplying the selected reference voltage to said internal circuit.
However, the above-mentioned prior art is designed to feed the power supply voltage from outside, and generate a plurality of reference voltages out of it and select one. A technique that can change the internal-power-supply-voltage by test modes in the semiconductor device having an internal power supply circuit has not been proposed yet.
The object of the present invention is to provide a semiconductor device having an internal power supply circuit that can change an internal-power-supply-voltage so that an accelerated test can be implemented effectively.
A semiconductor device having an internal power supply circuit according to the present invention, comprises: a substrate voltage detecting circuit which detects a substrate voltage of the semiconductor device having an internal power supply circuit and outputs the first level signal when the substrate voltage exceeds a reference voltage; a control circuit which lowers said substrate voltage when the output signal of the substrate voltage detecting circuit is switched to said first level; and a voltage setting circuit which inputs the first signal indicating a test mode and sets said reference voltage of said substrate voltage detecting circuit either lower or higher than that of normal operation.
This semiconductor device has a substrate voltage control circuit that inputs the second signal indicating a test mode and increases said substrate voltage, and the substrate voltage control circuit comprises a flip flop circuit that inputs said second signal, an output signal of said substrate voltage detecting circuit and a signal initializing a contact voltage when the voltage is supplied, a voltage conversion circuit that converts the voltage of the output signal given by the flip flop circuit, a resistance connected between said substrate and the ground, and transistors that are connected in series to said resistance and input the output of said voltage conversion circuit to the gates thereof, and is constituted so that in receiving said second signal, said flip flop circuit may be set, and in receiving the output signal of said substrate voltage detecting circuit, said flip flop circuit may be reset, enabling the substrate voltage to increase.
A semiconductor device having an internal power supply circuit according to the other aspect of the present invention comprises: a reference voltage generation circuit which generates a plurality of output signals of reference voltage; a selection circuit which makes a selection of said output signals in accordance with the first signals indicating a test mode; a voltage comparison circuit which compares the output signals of said selection circuit and the internal-power-supply-voltage; and an internal power supply control circuit which controls said internal-power-supply-voltage to the reference voltage in accordance with the comparison results given by the voltage comparison circuit.
In the case where the semiconductor device having this internal power supply circuit has a transistor that is connected between said internal-power-supply-voltage and the ground, and that inputs the second signals indicating a test mode via the gates thereof, and said test mode lowers the internal-power-supply-voltage, said second signals go high for a fixed period of time and cause said transistors to turn on for a fixed period of time and accordingly, the internal-power-supply-voltage to be able to be effectively lowered.
As explained above, since the present invention can change the internal-power-supply-voltage through the use of the first or second signals and set a substrate voltage or the internal-power-supply-voltage at a plurality of voltage, acceleration of tests can be effectively be realized.